Introduction The safety and efficacy of both abobotulinumtoxinA and onabotulinumtoxinA for upper limb spasticity are well established, but head-to-head comparisons are lacking. Methods DIRECTION is an international, randomized, double-blind, crossover study comparing the safety and efficacy of abobotulinumtoxinA with onabotulinumtoxinA in the management of upper limb spasticity at doses at or near maximum recommended in product labelling. Participants (18–75 years) will be randomized (1:1) to either one cycle of abobotulinumtoxinA (900U) followed by onabotulinumtoxinA (360U) or vice versa. To maintain blinding, a fixed volume (3.6 ml) will be injected into the target upper limb muscles (four wrist and finger flexors and biceps brachii). The second treatment cycle will begin at Week 12 if retreatment criteria are fulfilled, and if not, they will be reassessed every 4 weeks until they meet retreatment parameters. Planned Outcomes The primary hypothesis is that there is comparable safety between products; non-inferiority will be tested based on treatment-emergent adverse event (TEAE) rates from injection to Week 12. A secondary hypothesis is that abobotulinumtoxinA has longer duration of effect than onabotulinumtoxinA. This hypothesis will be tested with secondary efficacy endpoints, including injection cycle duration, Modified Ashworth Scale, Disability Assessment Scale and Physician Global Assessment. Trial Registration EudraCT ( http://eudract.ema.europa.eu ): 2021-000161-32 and Clinicaltrials.gov ( http://clinicaltrials.gov ): NCT04936542. Overview of the study protocol by the principal investigator (MP4 185265 KB) Supplementary Information The online version contains supplementary material available at 10.1007/s12325-021-01896-3.